On the effect of filters for the design of solid propellant gas generators

Solid propellant gas generator (SPGG) plays a role as a turbo pump starter in liquid propellant propulsion systems by supplying pressurized gas to power turbines for engine start. For such a purpose, the propellant should burn with a low flame temperature and the combustion gas should not contain corrosive constituents. Stabilized AN-based propellants have been used as the most appropriate propellant compositions that meet these requirements. However, because of its low burning rate, the burning area of the propellant intends to increase to satisfy the required mass flux and consequently the burning area increment brings on the SPGG size augmentation. A flow restriction such as filters, which are usually employed to filter off impurities in the combustion gas, is applied to decrease the SPGG size by rising up the combustion pressure resulting in increasing the burning rate. Pressure loss coefficient effects on the combustion pressure and on the SPGG/turbines system are investigated with the experimental results. Then the feasibility of the SPGG size reduction by the employment of filters has been studied. The preliminary results of this study show that the considerable reduction of SPGG size would be achievable just by installing a filter with a relatively high pressure loss coefficient.